[suggestion] Allows local disposable keys

[appetrosyan]

Currently disposable keys are bound globally. Given how they're supposed to be used, this is fine, but it might be better to allow them to be bound in a buffer-local context.

There's also the question of keymaps, but the way things work currently, is the bindings persist in a mode-specific keymap. I don't know if it's a good idea to consider adding extra keymaps for different major modes.